The Belize dollar is pegged to the USD at $2 Belize = $1 USD. So, the currency exchange is really easy for American visitors.
With this locked exchange rate, it’s quite simple to see how much something costs in USD when you go shopping.
In general accommodations are listed in USD prices, tours may be listed in both currencies, whereas restaurants, shops, etc. are usually listed in BZD.
The 2:1 exchange rate doesn’t apply if you exchange your US currency into Belize currency at the bank. The bank has a little lower exchange rate, so you’re better off using the US currency directly for shopping, at restaurants, etc.
Most all businesses readily accept US currency. Large bills (anything above a $20US) are a little more difficult to cash, especially if you as for change in USD.